Hi, my name is Jill and I'm an addict...

[Ross]

Welcome to the board! Glad you chose to join! Maybe we can be of help - maybe we can offer condolences

The pseudobulb you show does indeed look rotted, BUT, and I say - But, I have several Brassias with similar-looking bulbs that are doing just fine. So we aren't "out of the woods" yet, but maybe soon. A couple things stick out though. You say "north window". That's pretty dim for Oncidium. They really want a lot more light. Maybe not south, but at least east or west. Lights should be on approx the same length of day as you see outside. I adjust mine approx 1 hour more or less every other month.

Not sure on the white spots. Could be insects. But could also be residues from fertilizer, or something else. Need pics.

On the old Phal spike, I would cut it off, if it were mine. Think many here favor giving the plant time to regenerate.